As water Thursday night rose toward the brim of the reservoir behind the damaged spillway of Oroville Dam, state officials braced for the unprecedented: having to open the emergency outlet of the tallest dam in the United States, which could have untold ecological consequences.

The trouble started Tuesday in the midst of relentless rainstorms, as a section of the concrete spillway that later grew to more than 200 feet wide and 30 feet deep collapsed, frothing the Feather River below like chocolate syrup, so thick with mud and debris that those toiling to save millions of salmon at the hatchery below could hardly see two inches beneath the surface.

Officials stopped releases to inspect the problem but runoff kept the reservoir rising. On Thursday morning, officials increased the flow. The fissure ballooned outward, sending coffee-colored water gushing down the adjacent hillside.

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Allowing water to spill down the emergency spillway could be a necessity by Saturday if the level of California’s second-largest reservoir continues to rise, said Bill Croyle, deputy director of the California Department of Water Resources. But no one quite knows what that would do to the river and what lives in it.

The unlined emergency chute, which has never been called into use in the dam’s nearly 50-year history, would send deluges cascading down a neighboring hillside, taking into the river stray tree branches, dirt and anything else in the path of the liquid avalanche.

Appearances aside, Croyle said his team, with consultation from the U.S. Army Corps of Engineers, maintains the dam itself is sound.

“None of this emergency we have now is affecting the integrity of the dam itself,” Croyle said. “I think that’s important ... there’s no risk to the public.”

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Millions of fish raised at Feather River Hatchery below — ones crucial to California’s salmon stock — were not so lucky, as workers were scurrying to snap up in nets 4 million fish in danger of dying, and then trucking them miles downstream to safety. But nearly 5 million other fish and fish eggs couldn’t be moved.

The turbidity, or cloudiness, of the water running into Feather River Hatchery in Butte County, roughly 75 miles north of Sacramento, was “off the charts,” said Harry Morse, a spokesman for the California Department of Fish and Wildlife. Normal turbidity levels tend to be about 10 units, while Thursday’s recordings soared into the 400s, he said.

“This is just uncharted territory,” Morse said.

[center][/center]Workers were moving the millions of young fish, said to be about three months too young to safely release into the wild, about 10 miles down the river via giant tanker trucks to a facility at the Thermalito Afterbay far enough off the river that they should survive, Morse said.

Though water officials were releasing 35,000 cubic feet of water per second down the damaged spillway Thursday, with more pumped out via its power plant, it wasn’t nearly enough to cancel out the 191,000 cfs pouring into the reservoir from storm runoff, Croyle said.

In an effort to avoid needing to use the emergency spillway, Croyle said water experts were mulling increasing the flow to 55,000 cfs — similar levels to earlier in the week — but that could enlarge the gaping hole in the concrete spillway and worsen erosion that’s already unprecedented there.

[center][/center]Completed in 1968, the 770-foot dam provides water to large swaths of the state, including Central Valley farms and Southern California homes and businesses. The reservoir, which holds 3.5 million acre-feet of water, rose to more than 90 percent of its capacity Thursday evening.

Crews were working throughout the day to clear debris from the hillsides around both spillways — more than 50 acres of brush in all, officials said, trying to limit the debris that would join the flow if worse comes to worst.

Though fixing the “emergency” takes precedent, Croyle said state officials are eyeing already how to repair the massive structure, which would cost millions of dollars. Repairs likely won’t start for three months at the earliest, Croyle said.

“It’s key we understand what happened” before starting repairs, Croyle said, adding that officials are still examining what went wrong.

Inside the hatchery, which supplies fish that are later caught along the California coast and north up to Oregon, 1 million steelhead eggs, were in danger of being wiped out, Morse said.

[center][/center]The open concrete pools outside the hatchery, where the millions of evacuated fish lived — and where millions more still were trapped — take in water right from the river and were swamped with filth. The delicate fish eggs, which must be incubated in cold, clear water, are kept farther inside the facility behind filter defenses.

But the filters proved feeble in the face of the turbidity, and scientists inside scrambled to figure out how to safely mix tap water, which contains enough chlorine to kill the fragile eggs, with the cloudy river water that wasn’t much safer.

“This is a work in progress, and it has not been done before,” Morse said. “It’s ongoing as we speak.”

John McManus, executive director of the Golden Gate Salmon Association, said the Feather River Hatchery is “very important” to salmon production throughout California.

“It provides a lot of the fish that are caught in the ocean,” McManus said. “The loss of those fish would indeed be a blow to the salmon fishery.”

By 7 p.m. Thursday, the reservoir had risen to 887 feet, up 8 feet from the morning. After another 14 feet, the lake would be unleashed. And the water was rising.

“None of this emergency we have now is affecting the integrity of the dam itself,” Croyle said. “I think that’s important ... there’s no risk to the public.”

That's quite a statement, I wonder if he believes that. Guess he is not living downstream of the dam... Massive erosion like this and associated saturation can very quickly lead to a complete structural failure of a dam. Considering the enormous height (water pressure) and the potentially impacted neighborhoods downstream, that's catastrophic.

Also, this shouldn't be completely "uncharted territory" for the dam operators as they are required to have emergency plans and warning systems for these kind of scenarios.

Looks like they finally did the right thing and evacuated 188.000 people.

“You can withdraw from a climate agreement but not from climate change, Mr. Trump. Reality isn't just another statesman you shove away.”

It seems to me that once the emergency spill way over tops to a certain degree and given the fact it's all just soil in front of it it will quickly carve out a massive hole to the extent they won't have to worry about the dam since it will have drained down and either require a total re-build some such thing.

"If anyone loves the world, love for the Father is not in them. For everything in the world—the lust of the flesh, the lust of the eyes, and the pride of life—comes not from the Father but from the world." 1 John 2:15-16

The silliest thing and also most entertaining is speaking with people that don't believe or acknowledge their own hypocrisy.

"If anyone loves the world, love for the Father is not in them. For everything in the world—the lust of the flesh, the lust of the eyes, and the pride of life—comes not from the Father but from the world." 1 John 2:15-16